armature relation off center
This issue happens because your Grease Pencil object has transform data (location).

To fix this: first, in the Stroke tab, unparent the armature from your layer, otherwise the layer will move when you apply the new position.

Then use Ctrl+A or open the object menu and apply the necessary transforms (in this case, location). After this, your location data should revert to 0 but your drawings will stay in the same position. Then, parent the layers to the armature bones again.